In recent years, nitride semiconductor light emitting devices having a distributed Bragg reflector (hereinafter, referred to as DBR) which can selectively reflect light injected into a multi-layered film formed by laminating two layers having different refractivity alternately have been developed. Generally, the DBR is a reflector formed by laminating layers having a high refractivity and a low refractivity alternately and having a thickness of λ/(4n), wherein a wavelength of an aimed light in vacuum (air) is λ and a refractive index of a material is n. By this structure, in the light of a wavelength λ, there become in the same phase a wave which is reflected at a boarder between the high refractivity layer and the low refractivity layer when the incident light travels from the layer having a high refractivity to the layer having a low refractivity and a wave which is reflected at a boarder between the low refractivity layer and the high refractivity layer when the incident light travels from the layer having a low refractivity to the layer having a high refractivity, thereby a high reflectivity can be obtained. The reflectivity can be high with relatively small number of layers in case of laminating alternately two layers in which difference of refractivity is sufficiently large.
A laser device using nitride semiconductor as an example of a semiconductor light emitting device using the DBR is realized, as shown in FIG. 3, by forming, on a substrate 1, a buffer layer 9, an n-GaN contact layer 10, an n-type first light reflection layer 2, a light emitting layer forming portion 3 made with an active layer 32 sandwiched by an n- and p-GaN spacer layers 31 and 32, a p-type second light reflection layer 4, and a p-GaN contact layer 5, and providing a p-side electrode 8 on the p-GaN contact layer 5, and an n-side electrode 7 on an exposed portion of the n-GaN contact layer 10. The n-type first light reflection layer 2 and the p-type second light reflection layer 4 are formed by laminating a low refractivity layer 21 made of an n-AlGaN based compound (which means a compound in which a mixed crystal ratio of Al and Ga is not unequivocal and can be varied variously, and ‘based’, below means the same hereinafter) with a single layer structure and a high refractivity layer 22 made of an n-InGaN based compound with a single layer structure, respectively with a thickness of λ/(4n) (λ is a wavelength and n is a refractive index) and alternately (cf. PATENT DOCUMENT 1).    PATENT DOCUMENT 1: Japanese Patent Application Laid-Open No. H8-228048 (FIG. 3)